GB2268191B - Magnetostrictive material - Google Patents

Abstract

A magnetic material of at least two component parts arranged to have respective structures which mutually are not homogenous, the structure of one part cooperating with the structure of the other to assist the magnetostrictive behaviour of the material. The cooperation can be the structure of one part altering the atomic spacing of the other part [Fig. 1 Fig. 2] and the alteration can be an increase from the usual atomic spacing. A layer may have a lattice structure modified by an overlaid layer. The modification may be that the lattice of the second layer adopts at least approximately the lattice of the first layer. There can be contiguous component parts and the cooperation can be a pseudo free surface on at least one said part or a reduced restriction of the local moment otherwise achieved by the contiguous component parts [Fig. 5]. Reduction in the thickness of the layers has the effect of making the magnetorestriction more positive whilst annealing of the composite structure will also cause an increase of the magnetorestriction indicating that the metals of the layers, eg Fe and Co, have alloyed. A component can be at least partly an alloy and the alloy can have ratio other than the usual one for said alloy. One of the components can be non-magnetic eg Al, Mg, Ag, Au or SiO* subscript minus * or both can be magnetic eg Fe, Ni, Co, Gd, Tb.